"For men throughout evolutionary history, every missed opportunity to have sex with a new partner is potentially a missed reproduce opportunity - a costly loss from an evolutionary perspective." Haselton said.

"But for women, reproduction required much more investment in each offspring, including nine months of pregnancy and potentially two additional years of breastfeeding."

The consequences of casual sex were so much higher for women than for men, which likely shaped emotional reactions to sexual liaisons, she said.

In three studies, the researchers asked participants about their sexual regrets.

In the first study, 200 participants assessed fictional scenarios in which someone regretted pursuing, or failing to pursue an opportunity to have sex.

They were asked to rate their remorse on a five-point scale.

In the second study, 395 participants were given a list of common sexual regrets, and asked to point out which ones they had experienced.

The final study replicated the second study, but with a larger sample of 24,230 people, including bisexual and homosexual relationships.

More women than men included "having sex with a physically unattractive partner" as a top regret, at 17 per cent and 10 per cent respectively.

Though rates of having casual sex were similar between the participants, women reported more frequent and more intense regrets about it.

Haselton said for women, the emotional reaction might be far removed from the reproductive consequences faced in their ancestors' past.

"For example, we have reliable methods of contraception," she said.

"But that doesn't seem to have erased the sex differences in women's and men's responses, which might have a deep evolutionary history."

The peer-reviewed study was led by Andrew Galperin, a doctoral candidate in social psychology at University of California, Los Angeles.

Top three most common regrets for women:

- Losing virginity to the wrong partner (24 per cent)

- Cheating on a present or past partner (23 per cent)

- Moving too fast sexually (20 percent)

Top three most common regrets for men:

- Feing too shy to make a move on a prospective sexual partner (27 per cent)

- Not being more sexually adventurous when young (23 per cent)

- Not being more sexually adventurous during their single days (19 per cent)